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Full text of "Alaskan glacier studies of the National Geographic Society in the Yakutat Bay, Prince William Sound and lower Copper River regions"

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crevasses nowhere interfering with free travel over the ice surface. From this it is inferred that the glacier is moving very slowly. Much of the surface is darkened by fine morainic debris, but, excepting at the margin and in the narrow bands in the middle, there is no continuous morainic cover. In fact, when viewed from a distance, the glacier has the appearance of being entirely free from moraine, with the exception of medial and lateral moraines. No large tributaries to this glacier are visible, and it is certain that none but small tributaries enter from the south, for on this side there is only a narrow range of mountains with peaks that rise but six or seven thousand feet. There is a possibility that several tributaries of medium size enter from the north, and one tributary is shown in a Boundary Survey photograph of 1906. There can hardly be any large tributaries from this side, because the Variegated and Butler Glaciers head back in the mountains to the north, and so near as to cut off any possibility of long feeders to the Orange Glacier. The slight motion in the Orange Glacier is further indication of the absence of large tributaries. It was, therefore, suggested in the report of the 1905 and 1906 expeditions that this was in reality a wasting through glacier, a remnant of a former greater through glacier which crossed this divide from Nunatak Fiord to Russell Fiord in the neighborhood of Hubbard Glacier. In our expedition of 1909 we saw no reason for questioning this hypothesis, nor did we discover any additional facts bearing upon it.
Contrast with Variegated Glacier. Orange Glacier is of special interest from two different standpoints, both of which may be made clear by contrast with the conditions in Variegated Glacier. The first of these contrasts is the difference in the general characteristics of the two glaciers. The Variegated Glacier winds down through a deep mountain valley, then, emerging from its valley, spreads out at the mountain base in a broad, expanded piedmont bulb. Orange Glacier, so far as we have seen it, is a broad, slowly-moving, through glacier spreading down in both directions from the divide area. This through glacier terminates on each end without any notable expansion and without any considerable area of ablation moraine. There also seems to be a distinct difference in the source of the ice of the two glaciers. That giving rise to the Variegated Glacier is derived from snow slides and numerous, short, tributary glaciers from the steeply-enclosed mountains. The ice supply for Orange Glacier is also partly derived from the sliding of snow and the descending of short tributaries from the enclosing mountains, but a considerable portion of the supply, and perhaps the major part of it, is the snow that accumulates on the broad, fiat divide from which the ice descends eastward and westward.
The second noteworthy difference between the Orange and Variegated Glaciers is in then- behavior during the period of observation. Variegated Glacier, was subjected to a spasmodic advance by which its surface was broken from as far up the mountain valley as we could see, far down into the stagnant piedmont bulb, but before 1909 it had ceased to advance. Orange. Glacier, on the other hand, was in the same condition in 1906, as it was in 1905, and in 1909, 1910 and 1913 its condition had not changed. If this glacier is a wasting through glacier remnant there would be no reason to expect an advance in response to the earthquake shaking of 1899. If its ice supply comes mainly from the downsliding of snow and from short mountain tributaries, we should have expected some advance before 1910. The fact that there has been no such advance supports the interpretation of the origin of this glacier cited above. The only alternate hypothesis to account for the failure of this glacier to respond to the influence of earth-